Instagram

Path 2.0

Tumblr

Ustream

Pinterest

Industry-wide revenue for web publishers is projected to almost double in the next five years to almost $72 billion. Want to get in on the action? From Instagram to Path, take notes from the newest darlings in tech.

The photo-sharing app is the perfect example of scalability within this industry. Launched in 2010, Instagram, often praised for its elegant user-interface and superior mobile function, gained millions upon millions of users in 2011. The company does not generate revenue, but that didn't stop Facebook from acquiring it in April for a staggering $1 billion (shortly after the company received $50 million in Series B funding.) This year, the company captured its 40 millionth user.

Path proves that bigger isn't always better when it comes to social networks. Serial entrepreneurs Dustin Mierau, Dave Morin, and Shawn Fanning have positioned the app as a more intimate alternative to Facebook. Unlike other platforms, Path limits networks to 150 people to increase the quality of connections. Since its inception in late 2010, Path has accumulated more than 2 million users—half of whom joined after the app’s relaunch last December. The company, which raised more than $41 million in funding last year, is available on iPhone and Android devices.

In the last year, Tumblr has been the platform of choice for a number of key events, including the Occupy Wall Street movement and the launch of President Obama’s official 2012 reelection campaign. And those are just two of Tumblr's nearly 54 million blogs. The average Tumblr user creates 14 posts each month bringing the total post count to more than 22 billion. To date, the company has raised $125 million in funding.

Video is another sector of the industry with much growth potential. Look at Ustream, a service that broadcasts live programs like boxing matches, presidential debates, and red carpet events to viewers in the United States, Japan, and Korea. The company has raised $60.5 million to date, from Jeff Clavier, Infinity Venture Partners, SoftBank Capital, and others. Ustream integrated with Facebook Timeline in April and lets users stream events on television sets, computers, and mobile devices.

Practically overnight, Pinterest saw the kind of hockey-stick growth most start-ups can only dream about. The "virtual pinboard" racked up 10 million monthly users—mostly teens and women—in February, according to comScore. While some sources suggest that Pinterest's user figures may be leveling off, it hasn't stopped rumors that the start-up is the next big acquisition target. Meanwhile, the company has just raised $100 million in funding, putting it at a $1.5 billion valuation. Its reportedly venturing into the e-commerce space in the near future.